If think we can wonder if french was at some point the first language in Louisiana : past coastal and river towns, that weren't that much inhabited at first (in 1750's, around 3 200 inh.), then recieving a large non-francophone population ( in 1820's 41 000, the growth coming from both Antillas, slaves and slaveholders, and from non-french speaking migrants)...
If it happen, I'm not sure it wasn't only for a short time, between native language dominance and english.